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Next Step In Solid State Batteries

Solid-state battery technology has been in the news for a while, becoming increasingly relevant with the adoption of electric vehicles (EVs) and the unending growth in usage of portable electronic devices.

Everyone is on the lookout for smaller batteries that charge very quickly, are safe, and hold charge for long periods of time.

As we’ve looked at before, current lithium-ion batteries are limited by volatile and flammable liquid electrolytes. And there are a number of companies and research groups looking to address those limitations.

Significant progress has been made in solid-state technology over the last couple of years, replacing liquid electrolytes with a solid material, such as a polymer. This looks quite likely to be the next big step in battery technology. Interestingly, the man who took a giant leap 40 years ago and developed the technology that brought us lithium-ion batteries might be the one to do it again.

Glass To The Rescue

Recently, John Goodenough’s research lab at the University of Austin has grabbed attention after developing a solid state battery that can store three times as much energy as today’s lithium-ion batteries. Along with senior research fellow Maria Helena Braga, Goodenough designed a battery that replaces the liquid electrolyte with a specially engineered glass sheet (instead of a polymer).

The change may seem small, but the glass prevents ion movement across layers, suppressing the growth of metallic ion “whiskers” or dendrites, which can cause short circuits. These short circuits can lead to explosions, especially when the battery charges very quickly. It has been theorized that the Samsung Galaxy Note 7 battery explosions were due to this effect.

The glass electrolyte has also allowed the researchers to replace the electrodes with pure metal (in conventional cells, pure metal leads to rapid dendrite growth and failure). Using pure metal electrodes allows higher voltages and a higher energy density of the battery.

The cell can also be made with low-cost sodium instead of lithium; the former is plentiful and can be extracted from seawater, while the latter is currently often extracted using environmentally harmful metal mining techniques. The new design is also the first all-solid-state battery operating under 60˚C, and could operate at sub-zero temperatures, important for EV adoption in cold countries.

The Goodenough Effect

One of the reasons for the media interest in this discovery, apart from its obvious merits, is the connection with John Goodenough. At 94, he is going strong and remains one of the foremost figures in the field of battery technology. And as I hinted at earlier, this isn’t his first potentially game-changing invention.

In 1980, as a researcher at Oxford University, Goodenough invented a rechargeable battery using lithium cobalt oxide as the cathode, and lithium metal as the anode. The resulting lithium-ion battery is now the most common rechargeable battery for electronics like cell phones. If you’re reading this on a smartphone, you probably have Goodenough to thank.

Goodenough’s reputation precedes him. As Donald Sadoway, materials scientist at MIT told IEEE Spectrum, “When John Goodenough makes an announcement, I pay attention.” However, some researchers, including Professor Dan Steingart from Princeton University, have expressed doubts about the working of the new battery, questioning whether air had leaked into the cell, making it a “lithium-air” battery.

Lithium-air cells are extremely hard to make and rarely work for more than a few cycles. Lead researcher Braga has responded, “Well, if we have a lithium-air battery then we have a very good lithium-air battery”, since the group’s paper shows that the new cell ran for 1200 cycles.

While more will become clear about the Goodenough lab’s battery soon, it’s already apparent that solid-state energy storage technology is poised to become reality in the near future.